Crack Stitching using HeliBars
Stabilising cracked masonry using HeliBars and HeliBond grout
Masonry may move and crack for a variety of reasons. Seismic events are one cause. Foundation movement resulting from shrinkage and heave in foundation soils is another. Cracks may also continue to move and develop as a result of on-going seismic activity and cyclical wet and dry, hot and cold environmental conditions.
Crack stitching addresses the problem by reintroducing structural integrity and redistributing structural loads along the masonry to minimise further developments of the crack which may occur with simple injection methods.
Features and Benefits
- Quick, simple, effective and permanent
- Suitable for all types of masonry including listed and historic structures and those with lime mortar
- Austenitic stainless steel HeliBar reinforcing bars
- Fully concealed, non-disruptive repair system
- Cost-effective and more reliable than crack injection methods
- HeliBond is injectable and rapidly produces high compressive strength
- HeliBars and HeliBond grout produce excellent bond strength within the masonry
- HeliBars create great axial strength with flexibility
- No additional stresses are introduced
- Tensile loads are redistributed along the masonry
- Masonry remains flexible enough to accommodate natural building movement
- Minimises chances of the crack developing
- Reduces the likelihood of further cracking nearby
- Avoids any costly and disruptive taking down and rebuilding
- Permanent and sympathetic solution
- HeliBond cementitious grout
Repairing cracks near corners and openings
Where cracks are less than 500mm from an external corner (A) or an opening (B) at least 100mm should be bent around the corner and bonded into the return wall or bent and fixed into the reveal, avoiding any DPC membrane.
Points to Note
- The horizontal slots may be cut directly into the masonry but will typically be cut into the mortar beds when stitching face brickwork to ensure a hidden repair. The slots may be cut using a mortar chisel, brick saw, wall chaser or angle grinder with vacuum attachment (e.g. TV50 Vacuum and C-Tec Dust Guard).
- As standard, slots should be cut to 10mm in height to accommodate the 6mm diameter HeliBar. Each slot should be cut to the full mortar joint height, minimum 8mm, if cutting into the mortar bed. Contact Helifix for thin joint specifications.
- Multiple cracks may be stitched using single lengths of HeliBar that are long enough to extend 500mm beyond the outer cracks. Three cracks, each 250mm apart, may be stitched using 1.5m lengths of HeliBar, for example.
- All mortar must be removed, together with any loose debris, to ensure a sound bond.
- Prepare the slot with a water-based primer (e.g. HeliPrimer WB) or thoroughly wet the slot with clean water.
- HeliBond has been specifically engineered to produce a superior and durable HeliBar/masonry bond and is the recommended bonding agent. EpoxyPlus resin may used for smaller jobs or where loads are to be rapidly applied.
- Compatible with lime mortars.
Using an appropriate power cutting tool (see note A), rake out or cut slots into the horizontal mortar beds, to a minimum of 500mm either side of the crack, to the specified depth (typically 25-35mm) and at the specified vertical spacing (typically not more than four brick courses or 340mm apart).
Clean out the slots with a brush or blow pump and apply HeliPrimer or flush with water.
Using a finger trowel, or similar, push the HeliBar into the grout to obtain good coverage.
Insert a further bead of HeliBond over the exposed HeliBar, finishing 10-15mm from the face, and ‘iron’ into the slot using a finger trowel.
Repoint the mortar bed and make good.
Make good the vertical crack with an epoxy-based weatherproof filler, e.g. CrackBond
|Standard Material||Diameter||Length||Product Code|
|Grade 316 stainless steel||6mm||1m (standard) up to 7m||HBR6|
|Note: Typically, cracks will be best stitched using 6mm diameter HeliBar (HBR6). At this diameter, HeliBar can be installed into slots cut to a standard mortar joint height (approx. 10mm) without workmanship difficulties and without masonry disturbance. Multiple strands of HBR6 may also be run into individual slots to achieve particualr results. 8mm and 10mm diameters are also available, however, and may be used to suit unusual or particular circumstances. Contact Helifix for technical assistance.|
|INDICATIVE HELIFIX CRACK STITCHING SPECIFICATION|
|Cracked cavity (or veneer) wall|
|Spacing||2 - 4 courses (170-340mm approx.)|
|HeliBar Length||1000 mm|